Disclosed herein is a process for preparing diamide compounds having aromatic ester end groups. More specifically, disclosed herein is a process for preparing these compounds by a two-step process in the absence of a solvent in the second step using an organotin catalyst.
In general, phase change inks (sometimes referred to as “hot melt inks”) are in the solid phase at ambient temperature, but exist in the liquid phase at the elevated operating temperature of an ink jet printing device. At the jet operating temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the recording substrate, either directly or via an intermediate heated transfer belt or drum, they quickly solidify to form a predetermined pattern of solidified ink drops. Phase change inks have also been used in other printing technologies, such as gravure printing, as disclosed in, for example, U.S. Pat. No. 5,496,879 and German Patent Publications DE 4205636AL and DE 4205713AL, the disclosures of each of which are totally incorporated herein by reference.
Phase change inks are desirable for ink jet printers because they remain in a solid phase at room temperature during shipping, long term storage, and the like. In addition, the problems associated with nozzle clogging as a result of ink evaporation with liquid ink jet inks are largely eliminated, thereby improving the reliability of the ink jet printing. Further, in phase change ink jet printers wherein the ink droplets are applied directly onto the final recording substrate (for example, paper, transparency material, and the like), the droplets solidify immediately upon contact with the substrate, so that migration of ink along the printing medium is prevented and dot quality is improved.
The use of amide gellants in phase change inks is known, as disclosed in, for example, U.S. Pat. Nos. 7,714,040 and 7,625,956, the disclosures of each of which are totally incorporated herein by reference. Methods of making these materials are also known, as disclosed in, for example, U.S. Pat. Nos. 7,271,284 and 7,259,275, the disclosures of each of which are totally incorporated herein by reference. These amide gellants, when incorporated into radiation-curable phase change inks, enable advantages such as excellent adhesion to a wide variety of substrates and enhanced pigment dispersion stability.
While known compositions and processes are suitable for their intended purposes, a need remains for improved phase change ink compositions. In addition, a need remains for phase change inks that produce images with improved scratch resistance. Further, a need remains for phase change inks that produce images with improved adhesion to substrates such as paper. Additionally, a need remains for ultraviolet-curable compounds that can be incorporated into phase change ink carriers without adversely affecting the viscosity characteristics of the ink at desired jetting temperatures. There is also a need for ultraviolet-curable compounds that can be incorporated into phase change ink carriers without adversely affecting the melting point of the ink. In addition, there is a need for ultraviolet-curable phase change inks that can be used in ink jet printing processes wherein the ink is jetted directly onto a final substrate such as paper or transparency material. Further, there is a need for phase change inks that generate images which exhibit improved robustness on the final recording sheet. Additionally, there is a need for phase change inks that generate images with improved toughness. A need also remains for phase change inks that can be jetted at reduced temperatures. In addition, a need remains for phase change inks that enable control of dot spread of the ink, particularly in processes wherein the ink is jetted directly onto a final substrate. Further, there is a need for phase change inks wherein the ink does not bleed excessively into the substrate, particularly in processes wherein the ink is jetted directly onto a final substrate. Additionally, there is a need for phase change inks wherein the ink does not generate an undesirably high pile height and wherein an unnecessarily high number of drops are needed to create the image, particularly in processes wherein the ink is jetted directly onto a final substrate. A need also remains for phase change inks wherein the ink generates images with reduced showthrough. In addition, a need remains for phase change inks wherein the increased viscosity of the ink during photoinitiation reduces the rate of diffusion of oxygen and its inhibitory effect in the ink, thereby increasing the efficiency of cure. Further, a need remains for improved ultraviolet curable phase change ink compositions used in production printing. Additionally, a need remains for an improved phase change ink composition providing wide substrate latitude, excellent adhesion, and enhanced pigment dispersion stability. There is also a need for gellant compositions for phase change inks that can provide enhanced spectral transmission and gelation properties. In addition, there is a need for a gellant composition for phase change inks that can be readily produced and that does not require post reaction purification to achieve the desired gellant composition. Further, there is a need for a gellant that can provide adequate gelation strength without the need for complex processing steps. Additionally, there is a need for a gellant that has high thermal stability.
A need further remains for improved methods of preparing such gellants. Common methods for preparing these materials use a solvent-based esterification step using a Steiglich condensation reaction. The reagents used in this reaction include, for example, N,N-dicyclohexylcarbodiimide and N,N-dimethylaminopyridine. This process is solvent intensive and wasteful in that reactants such as the dicyclohexylcarbodiimide coupling reagent are expensive and generate significant solid urea waste byproduct. There exists a need for a ‘greener’, lower cost, faster and less wasteful process for making amide gellant molecules. There also exists a need for a method for making amide gellant molecules that enables a product with controlled polydispersity.